The spraying lavatory seat was introduced into Taiwan from Japan. Among the lavatory seats made in Japan, the "hot lavatory seat" and "sawayaka clean" made by Matsushita Electric are examples, wherein an electric heating wire is fixed into the bottom of the lavatory seat with a high cycle process after molding the seat, and the hot water for the sprayer is heated in a tank and led to the spraying position for spray.
The spraying lavatory seat previously designed in Taiwan comprises a hollow water trough casing at the bottom thereof. The hot water in the hot water trough flushing system fills up the trough so as to indirectly maintain the warmth of the lavatory seat. A hot water pipe is installed in the trough and is connected to a nozzle so as to directly spray the hot water.
In the foregoing hot lavatory seat having a water trough, the water trough cover is sealed with glue and will come off when hardened and subjected to water pressure, and the repeated turning up and down of the seat daily quickly results in leaking. This is a serious drawback frequently complained of the users of the seat.
In view of the above, the present inventor has previously designed an improved automatic lavatory seat (unlike the invention shown in the drawings) wherein an upwardly convex wall is provided at the perimeter of both inner and outer edges at the bottom of the seat to form a water channel. A recess is provided in the top surface of the wall to contain a sealing ring to prevent the water from leaking, and an inner cover in engagement therewith forms an enclosed water trough wherein such members as an electric heater, a heat-sensing bar, and a spraying pipe may be installed so as to heat the water therein, heat the seat, and supply a thermostatic spray. This improved device is described in Republic of China (Taiwan) Patent No. 72375.
The preceding improved device has been put into practice and marketed for one year, and is characterized by the "instant" spray of hot water. However, so far as the buildings in Taiwan are concerned, there is always only one water pipe leading from the roof to the ground floor and no pressure reduction valve is installed between adjacent floors. As a result, the water pressure of various floors varies and is extremely high at the lower floors. Since it is difficult to make the corners of the water trough sealing ring leak-proof, the air-tightness of the seats is poor in up to forty percent of the products (i.e., air enters the water trough). The electric heater immersed in the water trough for a long time tends to oxidize (rust) and to erode so that it leads to electric leakage (a factor which has been frequently exaggerated and criticized by Japanese manufacturers). The water trough of the above device is not a conduit with an even cross-section, so that a plurality of dead spaces form therein. These dead spaces retain air to mix with the water to form so-called "enclosed air," which results in a non-smooth spray. Furthermore, the air left in the water trough results in empty burning (i.e., heat sensing without water) of the electric heating pipe, which is dangerous. Otherwise, an air exhaust pipe for the dead space must be provided in the water trough, but this is prohibitive problem for the manufacturing process, resulting in a high cost--slightly cheaper than that of the seats made in Japan.
The Japanese spraying lavatory seat occupies a larger space and has a water heating tank to maintain the water therein at a mean temperature below 40.degree. C. at all times. When draining the water from the heating tank through the nozzle of the conduit, the cold water left in the conduit is sprayed first. This is a frequently criticized drawback.